1. Field of the Invention
The present invention relates to (1) a method of identifying an individual at an increased risk for developing cancer, (2) a method for determining a prognosis of patients afflicted with cancer, and (3) a method for determining the proper course of treatment for a patient afflicted with cancer.
2. Background Information
Lung cancer claims more lives in the United States than any other neoplasm (R. S. Finley, Am. Pharm. NS29, 39 (1989)), and of the various forms lung adenocarcinomas have one of the worst prognoses (T. P. Miller, Semin. Oncol. 17, 11 (1990)). The incidence of adenocarcinoma of the lung (ACL) in the United States is also quickly rising (I. Linnoila, Hematol. Oncol. North. Am. 4, 1027 (1990); J. B. Sorensen, H. H. Hansen, Cancer Surviv. 8, 671 (1989)). In order to gain insight into this complex and deadly disease, a model system for its study has been developed. For such a model to provide clinically relevant data several criteria must be met. The tumors produced should be histologically equivalent to their human counterparts, tumor induction must be reliable and reproducible, and the numbers generated must be great enough to provide statistical significance. To satisfy these conditions a system has been created which uses two inbred mouse strains (NFS/n and AKR) along with transplacental exposure to the potent carcinogen N-ethyl-N-nitrosourea (ENU) and promotion with the antioxidant butylated hydroxytoluene (BHT). The resulting tumors were examined for, altered expression or structural mutations of genes implicated in lung tumor development such as ras, myc, and raf oncogenes (C. D. Little et al., Nature 306, 194 (1983); P. E. Kiefer et al., Cancer Res., 47, 6236 (1987); E. Santos et al., Science 223, 661 (1984); S. Rodenhuis, N. Engl. J. Med. 317, 929 (1987); M. Barbacid, Eur. J. Clin. Invest. 20, 225 (1990); U. R. Rapp et al., J. Int. Assoc. for the Study of Lung Cancer 4, 162 (1988); M. J. Birrer et al., Ann. Rev. Med. 40, 305 (1989); G. Sithanandam et al., Oncogene 4, 451 (1989)).
raf proto-oncogenes are evolutionarily highly conserved genes encoding cytoplasmic serine/threonine specific kinases, which function in mitogen signal transduction (reviewed in U. R. Rapp et al., The Oncogene Handbook, T. Curran et al., Eds. (Elsevier Science Publishers, The Netherlands, 1988), pp. 115-154; U. R. Rapp, Oncogene 6, 495 (1991)). The three known active members in the raf family encode phosphoproteins of similar size (72/74 kD for Raf-1; 68 kD for A-Raf-1, and 74 kD for B-Raf (U. R. Rapp et al., in Retroviruses and Human Pathology, R. Gallo et al., Eds. (Humana Press, Clifton, N.J. 1985), pp. 449-472; T. W. Beck et al., Nucleic Acids Res. 15, 595 (1987); G. Sithanandam et al., Oncogene 5, 1775 (1990))). Raf-1 was first identified as the cellular homologue of v-raf (H. W. Jansen et al., Nature 307, 218 (1984)), the transforming gene of 3611 MSV (U. R. Rapp et al., J. Virol. 45, 914 (1983); U. R. Rapp et al., Proc. Natl. Acad. Sci. USA 80, 4218 (1983)). Amino acid comparisons of raf family genes shows three conserved regions [CR1, CR2, CR3] (T. W. Beck et al., Nucleic Acids Res. 15, 595 (1987)); CR1 is a regulatory region surrounding a Cys finger consensus sequence, CR2 is a serine/threonine rich region, and CR3 represents the kinase domain. Raf-1 has been mapped to chromosome 3p25 in humans (S. J. O'Brien et al., Science 223, 71 (1984)), and this region has been found to be frequently altered in small cell lung carcinoma (SCLC) (J. Whang-Peng et al., Cancer Genet. Cytogenet. 6, 119 (1982); J. M. Ibson et al., J. Cell. Biochem. 33, 267 (1987)), familial renal cell carcinoma (A. J. Cohen et al., N. Engl. J. Med. 301, 592 (1979); G. Kovacs et al., Int. J. Cancer 40, 171 (1987)), mixed parotid gland tumors (J. Mark et al., Hereditas 96, 141 (1982)), and ovarian cancer (K. Tanaka et al., Cancer Genet. Cytogenet. 43, 1 (1989)).
Raf genes are differentially expressed in various tissues (S. M. Storm et al., Oncogene 5, 345 (1990)). c-raf-1 has been found to be expressed ubiquitously, though absolute levels vary between tissues. A-raf-1 is present predominantly in the urogenital tissues, whereas B-Raf is most abundant in cerebrum and testis. The ubiquitous c-Raf-1 kinase is regulated by tyrosine and serine phosphorylations that result from activated growth factor receptor kinases (D. K. Morrison et al., Cell 58, 648 (1989); D. K. Morrison et al., Proc. Natl. Acad. Sci. USA 85, 8855 (1989); K. S. Kovacina et al., J. Biol. Chem. 265, 12115 (1990); P. J. Blackshear et al., J. Biol. Chem. 265, 12131 (1990); M. P. Carroll et al., J. Biol. Chem. 265, 19812 (1990); J. N. Siegel et al., J. Biol. Chem. 265, 18472 (1990); B. C. Turner et al., Proc. Natl. Acad. Sci. USA 88, 1227 (1991); M. Baccarini et al., EMBO J. 9, 3649 (1990); H. App et al., Mol, Cell. Biol. 11, 913 (1991)). Raf-1 operates downstream of Ras in mitogen signal transduction as judged by experiments using antibody microinjection (M. R. Smith et al., Nature 320, 540 (1986)), c-raf-1 antisense expression constructs (w. Kolch et al., Nature 349, 426 (1991)), dominant negative mutants (W. Kolch et al., Nature 349, 426 (1991)), and Raf revertant cells. Studies with NIH3T3 cells and brain tissue demonstrated that mitogen treatment induces Raf-1 kinase activity and causes a transitory relocation of the active enzyme from the cytoplasm to the nucleus and perinuclear area (Z. Ol ah et al., Exp. Brain. Res. (in press); U. R. Rapp et al., in Cold Spring Harbor Symposia on Quantitative Biology, Vol. LIII, Eds. (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. 1988) pp. 173-184).
Raf-1 coupling has been examined in more than a dozen receptor systems and all strong mitogens stimulated Raf-1 kinase activity (U. R. Rapp, Oncogene 6, 495 (1991); D. K. Morrison et al., Cell 58, 648 (1989); D. K. Morrison et al., Proc. Natl. Acad. Sci. USA 85, 8855 (1989); K. S. Kovacina et al., J. Biol. Chem. 265, 12115 (1990); P. J. Blackshear et al., J. Biol. Chem. 265, 12131 (1990); M. P. Carroll et al., J. Biol. Chem. 265, 19812 (1990); J. N. Siegel et al., J. Biol. Chem. 265, 18472 (1990); B. C. Turner et al., Proc. Natl. Acad. Sci. USA 88, 1227 (1991); M. Baccarini et al., EMBO J. 9, 3649 (1990); H. App et al., Mol. Cell. Biol. 11, 913 (1991)), and this stimulation correlated with an increase in Raf-1 phosphorylation leading to a shift in apparent molecular weight.